1. Field of the Disclosure
The present disclosure relates to polyglycerol-azelaic acid polyesters and their applications in the field of cosmetics.
2. Discussion of the Background Art
Azelaic acid is dicarboxylic acid with the IUPAC name nonanedioic acid and the structural formula (I) shown below:

This acid can be produced from oleic acid (cis-9-octadecenoic acid), a monounsaturated fatty acid, by ozonolysis followed by oxidative cleavage; during the reaction they form an azelaic acid molecule and a nonanedioic acid molecule.
Azelaic acid has been proven to be particularly effective in the topical treatment of comedonal acne and inflammatory acne (papulopustular, nodular and nodulocystic). Its use was developed from the observation that species of the Pityrosporum ovale (Malassezia furfur) genus are able to oxidise the unsaturated fatty acids present in sebum to dicarboxylic acids which competitively inhibit the tyrosinase enzyme. Due to its inhibitory effect against tyrosinase, the compound has also been used to treat melasma, lentigo maligna, hyperpigmentation and other diseases characterised by the abnormal proliferation of melanocytes.
Azelaic acid is also proven to be effective in treating hypermelanosis caused by physical and photochemical agents, with no evident lightening action on normal skin and without being photosensitising.
This acid has also shown a selective antiproliferative and cytotoxic effect on human malignant melanocytes (as is discussed in the article “Azelaic acid. A review of its pharmacological properties and therapeutic efficacy in acne and hyperpigmentary skin disorders”, Fitton A., Goa K. L. Drugs 1991 May; 41 (5):780-98). The mechanism of this action is still unclear although it may be related to the ability of azelaic acid to inhibit mitochondrial oxidoreductase activity and DNA synthesis.
A problem related to the use of azelaic acid in topical formulations is that this acid, like other short-chain dicarboxylic acids, has an irritant effect when in contact with the skin; this side effect, which is generally temporary, may manifest itself as itching or tingling. The information contained in the literature indicates that the irritation potential of these substances decreases with increasing alkyl chain length, although longer chains do not retain the positive primary effects of azelaic acid illustrated above.
There is therefore a need for compositions which are able to deliver azelaic acid, whilst substantially reducing or eliminating the side effects.